Compound bearing an urethane linkage which is an adduct of ricinoleic esters and an isocynate, useful as a plasticizer for polyvinylchloride (PVC) and a process for preparing such compound

ABSTRACT

A novel compound bearing urethane linkage of formula as shown herebelow, which is an adduct of ricinoleic ester and isocyanate, useful as a plasticizer for polyvinylchloride (PVC) and a process for the preparing the compound bearing urethane linkage by reacting fatty acid esters bearing hydroxyl groups with an organic isocyanate in the presence of a catalyst at a temperature in the range of 30°-100° C. ##STR1## Wherein Ar= ##STR2##

This invention relates to a novel compound bearing an urethane linkageuseful as a plasticizer for polyvinyl chloride (PVC) and a process forpreparing the compound. This compound is an adduct of ricinoleic estersand an isocyanate, which is prepared by the process of the presentinvention is new and has formula 1. ##STR3## wherein Ar is selected fromthe group consisting of ##STR4##

The invention specifically relates to a process for the preparation of acompound bearing an urethane linkage useful as a plasticizer for polyvinylchloride (PVC). The compound prepared by the process of the presentinvention is new and has the formula 1. The compound of formula 1, isderived from a fatty acid ester bearing a hydroxyl functionality and/orcompound containing isocyanate functionality. More specifically, theinvention relates to a process for the preparation of urethane typecompound of formula 1 having molecular weight in the range of 650 to900.

The compound of formula 1, prepared by the process of the presentinvention has excellent compatibility with PVC on account of thedesirable functional groups present in the molecule. Hence, theinvention further provides a process for the preparation of improvedcompounded PVC employing the urethane type compound of formula 1.

It is well known in the prior art that addition of organic compounds,called plasticizers, to PVC confers on the PVC desirable properties suchas flexibility, softness, good feel and ease of processability,extensibility and lower melting temperature Encyclopedia of PVC Vol. 1and 2, L. I. Nass (1976)!. Plasticizers function by dissolving in PVC,reducing the cohesive energy density between the polymer chains andreducing the polar forces exerted by the halogen atoms present in PVC.For any organic compound to function as an effective plasticizer for PVCit must possess (a) very high miscibility with PVC, (b) must have polargroups and (c) must have a low tendency to diffuse and migrate out ofthe polymer during its effective service life. In addition, theplasticizer must not cause colouration to PVC, should be non toxic,odorless, possess low volatility and thermally stable at the temperatureof mixing and compounding PVC with plasticizer.

A variety of organic compounds have been reported as effectiveplasticizers for PVC. These include esters of phthalic anhydride withaliphatic alcohols (linear/branched) with four to fifteen carbon atoms,epoxidized soyabean oil, esters of trimellitic acids, phosphates, estersof benzoic and citric acids, and halogenated hydrocarbons. Highermolecular weight polyesters (800-6000) prepared by condensation of diolswith adipic or sebacic acids are also used as plasticizers. Of these,phthalate based plasticizers are the most widely used because of theirexcellent compatibility with PVC, ease of fusion and all round desirableproperties.

Nevertheless, phthalate esters are not without drawbacks.Dioetylphthalate has been implicated as a carcinogen causing livercancer in rats. Their molecular weights are low on account of which theydiffuse out of PVC rapidly and cause "fogging" (cloudy dsposits) ofglasses and other transparent surfaces. They are easily extracted byorganic solvents, making them unsuitable for use in solvent contactapplications. They produce PVC products whose surface resistivity isvery high (approximately 4×10¹⁴ Ω at 30° C.) for many applications suchas antistatic products for hospitals flooring materials, footwear,hoses, clean room fixtures, trays for integrated circuits and floppydiscs, conveyor belt etc. The surface resistivity can be brought down bya factor of 10¹ -10² by adding an antistat additive (example Irgastat 51of Ciba Geigy). However, use of such additives leads to loss ofdesirable properties of PVC. The thermal and light stability isadversely affected and the antistatic additive exudes out of PVC.

To overcome the above problems envisaged in the prior art, theapplicants have now provided a novel compound bearing an urethanelinkage shown in formula 1, which is useful as a plasticizer for PVC; aprocess for preparing such compound and, a manner in which a compoundedPVC is prepared by employing the novel compound.

Therefore, one object of the present invention is to provide a compoundhaving an urethane linkage of formula 1.

Another object of the invention relates to a process for the preparationof new plasticizer for PVC.

Yet another object of the present invention is to provide a process forthe preparation of new plasticizer derived from fatty acid esters and ahydroxyl group, and an isocyanate bearing organic compound.

Still another object of the present invention is to provide a processfor the preparation of improved compounded polyvinyl chloride using thecompound of formula 1 as a primary plasticizer. The use of compound offormula 1 in conjunction with PVC confers on PVC many desirableproperties such as flexibility, softness, good mechanical and thermalproperties. In addition, use of compound of formula 1 eliminates many ofthe drawbacks of the hitherto known plasticizers for PVC.

Further object of the invention is for a compounded PVC comprisingpolyvinyl chloride and a plasticizer of formula 1.

In the course of the applicants research, they have developed a processfor the preparation of a new organic compound of the formula 1 whichshow useful properties as primary plasticizer for PVC. The compound offormula 1 is derived from the reaction of fatty acid esters havingeighteen carbon atoms and a hydroxyl group, and organic isocyanates.

The fatty acid esters suitable for the present invention are esters ofricinoleic acid and 12 hydroxyl stearic acid. The ester can be derivedby reacting ricinoleic acid or 12 hydroxystearic acid with an alcoholhaving a linear or branched alkyl group having 1-10 carbon atoms.

The isocyanate useful in the process of the present invention can beselected from any organic isocyanates having one or two isocyanategroups per molecule. Examples are toluene diisocyanate of formula 3,##STR5## 4,4'-diisocyanatodiphenylmethane of formula 4, ##STR6##1,4-diisocyanatobenzene of formula 5, ##STR7## hexamethylenediisocyanate of formula 6,

    OCN--(CH.sub.2).sub.6 --NCO                                (FORMULA 6)

isophorone diisocyanate of formula 8, ##STR8##1,4-diisocyanatocyclohexane of formula 7. ##STR9## The preferredisocyanates are those derived from aromatic compounds and having atleast two isocyanate groups.

Accordingly, the present invention provides a novel compound bearingurethane linkage having formula 1.

The invention also provides a process for the preparation of a compoundbearing urethane linkage having formula 1 useful as a plasticizer forPVC which comprises reacting fatty acid esters bearing hydroxyl groupswith an organic isocynate at a temperature in the range of 30-100° C. inthe presence of a catalyst. The molar ratio of hydroxyl bearing fattyacid to the isocyanate may be in the range of 2:1.1, the preferred ratiobeing 2:1.05. The catalyst employed in the reaction may be selected fromany one of the following: di-n-butyltindilaurate, di-n-butyl-tinoxide,1,4-diazabicyclo 2.2.2! octane (DABCO), 4', 4'-dimethylamino pyridine(DMAP) and 1, 8-diazabicyclo 5.3.0! undec--7--ene (DBU). Theconcentration of the catalyst may range from 0.02-0.2% by weight of theisocyanate compound. The preferred concentration is in the range of0.05%. The reaction is conducted for a period of 1-3 hours. The progressof the reaction is monitored by Brookfield viscosity and determinationof hydroxyl number. The final product should have a viscosity below 2500centipoises at 27° C. and have a hydroxyl number below 20 (expressed asmg KOH/g). The product molecular weight as measured by vapour pressureosmometry is in the range of 650-900 depending on the nature of theisocyanate.

The process of preparing the plasticizer is clean, does not produce anyeffluents or by-products and is ready for use at the end of the reactiondirectly without any further processing.

The structures of the compounds prepared by the process of the presentinvention have been established by a variety of spectroscopic techniquessuch as infra red, nuclear magnetic resonance and mass spectrum. Morespecifically, a product derived from the reaction of ricinoleic acidmethyl ester with toluene diisocyanate shows in infra red spectrumabsorption at 3320, 1730-1750, and 1400-1600 inverse centimeters due to--NH, carbonyl and --HC═CH-- groups. The nuclear magnetic resonanceshows peaks at 0.9-2.5, 3.6-3.7, 5.0-6.0 and 6.5-7.5 ppm correspondingto the methyl groups, methoxy group, vinylic hydrogen and aromatichydrogen attached to ring.

The invention further provides a process for the preparation of acompounded PVC, which process comprises mixing a compound of formula 1at a temperature in the range of 120° to 150° C. and in the presence ofa stabiliser and if desired, preparing the sheets of the compounded PVC,so prepared, of the desired dimensions by conventional methods.

The advantages of using the compound of the formula 1 are:

1. The compound is compatible with both PVC and phthalate typeplasticizers, enabling its use either by itself as a primaryplasticizers or in blends with phthalates, if necessary.

2. It has a high molecular weight and thus low tendency to migrate orexude from the surface.

3. It is derived from naturally occurring fatty acids and possessurethane type linkages, which has been established in the prior art asbiocompatible (Ref: Japan Patent 7650,958 dated May 6, 1976 to DainipponInk and Chemicals Inc.). Hence, the plasticizer should show very lowtoxicity.

4. Its polar character makes it poorly soluble in organic solvents.Hence PVC plasticized by compounds of formula 1 show excellentresistance to extraction by organic solvents.

5. PVC plasticized by plasticizers of formula 1 show exceptionally lowsurface resistivities (6×10⁹ Ω30° C.) without addition of any antistaticadditives.

The plasticizer, prepared by the process as described above iscompounded with PVC in an electrically heated two roll mill in presenceof stabilizers to form a smooth sheet of 150 mm×150 mm×2 mm size. Thecontent of plasticizer used may be in the range of 40 to 60 parts perhundred parts of the resin (phr). The preferred composition is 50 phr.The urethane plasticizer can also be incorporated in blends with estertype plasticizers well known in the prior art. For example, urethaneplasticizer can be blended with di-2-ethylhexylphthalate (DOP) in anamount ranging from 10:90 to 90:10 proportions prior to incorporation inPVC. The stabilizers added are chosen from a variety of metal stearateswell known in prior art. The metal stearates can be derived from barium,cadmium, calcium, zinc and the like. The concentration of thestabilizers is in the range of 1-5 phr, preferred concentration being 3phr. The dry blend of PVC, plasticizer and the stabilizers are mixed ina two roll mill at the temperature range 120-150° C. for 2-10 minutes,till complete and uniform fusion of the blend occurs. The sheet is thenused for preparing test specimens which are tested for properties as permethods prescribed by American Society of Testing Materials (ASTM). Theresults are shown in Table 1 where the performance of the urethaneplasticizer is compared with di-2-ethylhexylphthalate (DOP) underidentical conditions (Table 1). The mechanical as well as high and lowtemperature properties of urethane and DOP plasticizers are essentiallysimilar. However, dramatic improvements are observed with regard toextractability in organic solvents and surface resistivity. The resultsconfirm that the compound of formula 1, is a primary plasticizer for PVCand possesses useful properties which are not present in DOP typeplasticizers.

                  TABLE 1    ______________________________________    COMPARATIVE PROPERTIES OF COMPOUNDED PVC USING    URETHANE PLASTICIZER AND DOP.sup.a                         Value    Property   Test method                          Unit     Urethane.sup.b                                          DOP.sup.c    ______________________________________    Hardness,  ASTM D-2240                          --        78     79    Shore A    Tensile strength               ASTM D-412 kg/cm.sup.2                                   220    212    Modulus, 100%               ASTM D-412 kg/cm.sup.2                                   133    131    Elongation at               ASTM D-412 %        370    340    break    Surface resistivity               BS 2050    Ω  6 × 10.sup.9                                          3.8 × 10.sup.14    30° C.    Glass transition      ° C.                                   -26    -31    temperature    Heat loss at          %        0.8    0.6    130° C., 3 hr    Extraction test,               ASTM D-1239    wt. loss    i)  Water, 35° C.  %      0.3     0.03        24 hr    ii) Kerosene,             %      2.6     44        24 hr    ______________________________________     .sup.a PVC resin (K = 65), 100 phr, compounded with plasticizer 50 phr an     stabilizers 3 phr; sheet thickness: 30-35 mil.     .sup.b Compound of formula 1 prepared by the reaction of ricinoleic acid     with toluenediisocynate.     .sup.c Di2-ethylhexylphthalate

The invention is described in detail in the examples which are providedby way of illustration only and therefore should not be construed tolimit the scope of the invention.

Examples 1 to 5 relate to the preferred processes for preparing a fewcompounds bearing urethane linkage and examples 6 to 9 are for thepreferred processes of preparing plasticized PVC.

EXAMPLE 1

In a 2 liter four neck round bottom flask equipped with mechanicalstirrer, thermowell, gas bubbler and dropping funnel two moles of methylricinoleate of formula 9 ##STR10## and 0.5 g of dibutyl tin dilaurateare taken. The flask is mounted in a 2 L capacity heating mantle, theheating of which can be suitably controlled. With continuous stirring ina stream of nitrogen has 0.9 mole of toluene diisocyanate (TDI) offormula 3 is added dropwise from the dropping funnel, care being takennot to allow the temperature of the reaction flask to increase above 30°C. After the addition of TDI is over which lasts for about an hour, thecontents of the flask are heated to 70° C. and maintained at 70° C. forone hour. As soon as addition of TDI is over, a sample is drawn forpercentage isocyanate determinations. Two more samples, one after halfan hour and another after one hour after the complete addition of TDIare drawn for percentage isocyanate determination. It is observed todecrease periodically and reaches minimum after about one hour heatingat 70° C. Viscosity of the material is observed to increase during thecourse of the reaction and heating is stopped after one hour at 70° C.The colour, acid value, --OH value, viscosity and molecular weight ofthe product which is a Benzene, 2, 4 diisocyanato-1-methyl adduct and9-octa decenoic-12 hydroxy methyl ester of the formula 1 wherein Arrepresents formula 3, are observed to be 200 (APHA), 0.25 mg.KOH/gm, 18mg.KOH/gm, 2,400 centipoises and 850 respectively.

EXAMPLE 2

In a 2 (liter) four neck round bottom flask equipped with mechanicalstirrer, thermowell, gas bubbler and dropping funnel 2.1 moles of12-hydroxy methyl stearate of formula 10 ##STR11## and 0.35 g ofdi-n-butyl-tin dioxide are taken. The flask is mounted in a 2 L capacityheating mantle, the heating of which can be suitably controlled.

With continuous stirring and in a stream of N₂ gas, one mole of toluenediisocyanate of formula 3 is added dropwise through the dropping funnel,care being taken not to allow the temperature of the reaction mixture toexceed 30° C. After the addition is over, which lasts for about an hour,a sample of the reaction mixture is withdrawn for percentage isocyanatedetermination and the flask is heated to 70° C. and maintained at 70° C.After half an hour at 70° C., another sample is drawn for % NCO andhydroxyl value determination. Similarly after heating at 70° C. for onehour anothersample (benzene 2.4 diisocyanate-1-methyl adduct ofoctadecenoic-12-hydroxy methyl ester of formula 2) ##STR12## is drawnfor percentage isocyanate and hydroxyl value determination. After totalheating period of one hour at 70° C. the contents are cooled and theproduct of formula 2 which is a Benzene 2, 4 diisocyanato-1-methyladduct of octa decenoic acid 12-hydroxy methyl ester of formula 2analysed for colour, acid value, hydroxyl value, viscosity and molecularweight which are found to be 150-200 (an index of color as specified byAmerican Public Health Association-APHA), 0.3 mg.KOH/gm, 12 mg.KOH/gm,1480 centipoises and 855 respectively.

EXAMPLE 3

In 1 L (liter) four neck round bottom flask equipped with mechanicalstirrer, thermowell, gas bubbler and dropping funned two moles of butylricinoleate of formula 11 ##STR13## and 0.35 g of dibutyl tin-dilaurateare weighed and the flask is mounted in a 1L capacity heating mantle, ofwhich heating can be suitably controlled. Then with continuous stirring,in a stream of nitrogen gas, 0.95 mole of toluene diisocyanate offormula 3 of the drawings is added dropwise through the dropping funnel.The additionwhich lasts for about 40 minutes is carried out maintainingthe temperature of the flask below 30° C. After the addition is over theflask is heated to 70° C. and maintained at 70° C. for one hour. Duringthis period of one hour two samples are drawn at the interval of 30minutes each for percentage isocyanate and hydroxyl value. Both % NCO,as well as --OH value are observed to decrease whereas viscosity of thecontents is observed to increase during the course of his reaction.After one hour heating at 70° C., the contents benzene2.4-diisocyanate-1-methyl adduct of 9-octadecenoic and 12-hydroxy butylester are cooled, discharged in a stoppered container and the compoundof the formula 1 which is analyzed for colour, acid value, hydroxylvalue, % NCO viscosity and molecular weight, which are observed to be200 APHA, 0.71 mgKOH/gm, 10.79 mgKOH/gm, 0.83, 1920 centipoises (27 C)and 750 respectively.

EXAMPLE 4

In a 500 mL capacity four neck round bottom flask equipped withmechanical stirrer, thermowell, gas bubbler and dropping funnel 350 gmbutyl ricinoleate of formula 11 and 0.35 g of dibutyl tin dilaurate aretaken and the flask is mounted in a constant temperature oil bath, thetemperature of which can be suitably controlled. From the droppingfunnel 111.0 g iso-phorone diisocyanate (IPDI) of formula 8 is addeddropwise with continuous stirring in a stream of nitrogen gas. Theaddition which lasts for about an hour is done at 27° C. After theaddition is over, the contents i.e. 3-isocyanato methyl 3, 5,5-timethyl-cyclo-hexyl isocyanate adduct of butyl ricinoleateare heatedto 70° C. and maintained at 70° C. for one hour, after which the flaskis cooled to room temperature and the compound of the formula 1viscosity and molecular weight which are found to be 50 APHA, 0.5 mgKOH/gm, 15 mg KOH/gm, 0.5, 2200 centipoise (27° C.) and 820respectively.

EXAMPLE 5

In a 500 mL capacity four neck round bottom flask equipped withmechanical stirrer, thermowell, gas bubbler and dropping funnel 0.22moles methylricinoleate of formula 9 of the drawings and 0.04 gm ofdibutyl tin oxide are taken. The flask is mounted in a constanttemperature oil bath and with continuous stirring, in a stream of N₂,gas 0.1 moles of hexamethylene diisocyanate of formula 6 is addeddropwise through the dropping funnel, temperature of the flask beingmaintained below 30° C. during the course of addition. After theaddition is over, the contents i.e. hexamethylene isocyanate adduct ofmethyl ricinoleate are heated to 50° C. for one hour and then cooled toroom temperature and the compound of the formula 1 analysed for colour,acid value, hydroxyl value, % isocyanate, viscosity and molecularweight, which are found to be 50 APHA, 0.4 mg KOH/gm, 21,2 mg KOH/gm,0.32, 1800 centipoises (27° C.) and 800 respectively.

EXAMPLE 6

In a 250 mL beaker, 50 g of polyvinyl chloride of K-65 grade, 25 g ofplasticizer derived from toluene diisocyanate and methylricinoleate(from ex:1), 0.5 g stearic acid and 1.5 g of Ba--Cd stearate asstabilizer are weighed and mixed thoroughly with the help of a spatuala.Then the material is mixed in a two roll PVC mixing mill for 5 minutes.The rolls are maintained at 140±2° C. during mixing. After completefusion of PVC and thorough mixing of plasticizer and stabilizer, acontinuous band is obtained on the roll which is cut repeatedlyhorizontally and mixed thoroughly. A continuous sheet of about 3 to 4 mmis obtained at the end.

From this, a smooth sheet of 150 mm×150 mm×2 mm size was obtained bycompression moulding in a hydraulic press at 165° C. for five minutes.The test specimens for mechanical property evaluation were cut usingsuitable die as per American Society of Testing Materials (ASTM) D--412.The hardness, tensile strength, 100% modulus, elongation at break of thecompounded PVC sheet are found to be 78 (shore A) 220 kg/cm², 133 kg/cm²and 370% respectively.

EXAMPLE 7

In a 250 mL beaker 120 g polyvinyl chloride powder of K-65 grade, 41 gof a plasticizer derived from toluene diisocyanate and methylricinoleate, 1.2 g stearic acid and 2 g of Ba--Cd stearate as thestabilizer are weighed and mixed thoroughly with the help of a spatuala.Then the mixture is compounded by milling in a two roll PVC mixing millat 140±2° C. for five minutes. Initially the material softens on theheated rolls and fuses to form a band around one of the rolls of themill. The band is cut repeatedly by a knife in horizontal direction andthe sheet is obtained repeatedly. After forming a smooth, band, it iscut and an uniform sheet of about 3 to 4 mm thickness is obtained.

This sheet is used for compression moulding (at 165° C. for five minutesat 1800 psi pressure) to set an uniform smooth sheet of 150 mm×150 mmsize.

The test specimens for the property evaluation were punched out fromthis sheet. Using suitable die as per American Society of TestingMaterial (ASTM) D--412, and were found to give Shore A hardness, tensilestrength, 100% modulus and elongation at break as 80, 262.5 kg/cm²,187.1 kg/cm² and 300% respectively.

EXAMPLE 8

In a 250 mL capacity beaker 100 g polyvinyl chloride powder of K-65value, 44 g of urethane plasticizer, derived from toluene diisocyanateand methylricinoleate, 2 g of Ba--Cd stearate stabilizer and 1 g ofstearic acid as the lubricant are weighed and mixed thoroughly bystirring with the help of spatuala. The contents of the beaker aremilled in a two roll PVC mixing mill at 140° C. for five minutes. Therolls of the mill are heated electrically. Initially the PVC powdersoftens while in contact with the rolls and on complete fusion it formsa continuous band over one of the rolls. The continuous band is cutrepeatedly and mixed thoroughly to give good dispersion of plasticizerand stabilizer in the PVC sheet. Finally, by having a horizontal cut,continuous, uniform sheet of the compounded material having 3 to 4 mmthickness is obtained.

A suitable sheet of size 150 mm×150 mm×2 mm is obtained by compressionmolding of the compounded sheet for five minutes at 165° C. and at 2000psi.

The test specimens for property evaluation were punched out from thesheet using suitable dies as per ASTM specifications. The Shore Ahardness, tensible strength, 100% modulus and elongation at break werefound to be 78, 225 kg/cm², 132 kg/cm² and 330% respectively.

EXAMPLE 9

In a 500 mL beaker 140 g of polyvinyl chloride (PVC) powder of K-65value, 77 g of urethane plasticizer, derived from toluene diisocyanateand methylricinoleate, 4 g of Ba--Cd stearate as stabilizer and 1 g ofstearic acid as lubricant are weighed and thoroughly mixed by stirringwith spatuala. The contents are milled in a two roll PVC mixing mill at140° C. for five minutes. A uniform sheet is formed on one of the rollsafter softening, and fusion of PVC with the plasticizer and stabilizerwhich is cut horizontally several times and milled to get good sheet of3 to 4 mm thickness. This sheet is used to get uniform and smooth sheetof 150 mm×150 mm×2 mm size by compression moulding at 165° C. for 2minutes and at 1800 psi pressure. The test specimens for propertyevaluation were punched out using suitable die as per ASTM and theproperties such as Shore A hardness, tensile strength, 100% modulus andelongation at break were observed to be 75, 220 kg/cm², 133 kg/cm² and390% respectively.

We claim:
 1. A composition of matter consisting essentially for a novelcompound of the following formula: ##STR14## wherein Ar is selected fromthe group consisting of Ar═! ##STR15## which is an adduct of ricinoleicacid and an isocyanate.